1. Field of Invention
The present invention relates to a shift register circuit and a display device using the same.
2. Related Art
Since the flat display device such as liquid crystal display (LCD) device or AMOLED (Active Matrix Organic Light Emitting Diode) display device has the advantages, such as thinner, lighter, lower power consumption, less radiation, compatible with semiconductor manufacturing processes, etc., it is widely applied to various electronic products.
In order to decrease the size of the flat display device, the driving circuit can be integrated onto the substrate of the flat display device. For example, the shift register circuit can be formed directly on the substrate of the LCD or OLED panel. However, in order to mitigate the undesired influence caused by the leakage current of thin film transistor (TFT), especially Indium-Gallium-Zinc Oxide TFT (IGZO TFT), the shift register is usually configured with additional TFTs.
FIG. 1 is a circuit diagram showing a conventional shift register, and FIG. 2 is a schematic graph showing I-V curve of TFT in FIG. 1. Referring to FIG. 1, a shift register includes fifteen n-type thin film transistors (TFT) and seven capacitors. This shift register can be applied to the scan driving circuit or the data driving circuit of the active matrix liquid crystal display or active matrix OLED display. After receiving the carry signal, the shift register then outputs a pulse signal and transfers the carry signal to the next shift register.
The TFTs of the shift register in FIG. 1 is implemented with IGZO TFTs. Although the shift register in FIG. 1 can avoid the drawback of IGZO TFT that the threshold voltage is negative as shown in FIG. 2, this shift register needs considerable amount of TFTs and capacitors. Because these components are comprised so as to make the TFT properly turn off and on, it causes that the layout of the entire shift registers is really huge. Thus, it is difficult to make the frame of the display panel thinner.
Therefore, it is an important subjective of the present invention to provide a display device and shift register which can transmit signals with compact electronic elements and less electric noise.